Search results for "WAF"

Photoluminescence Imaging and LBIC Characterization of Defects in mc-Si Solar Cells

2018

Today’s photovoltaic market is dominated by multicrystalline silicon (mc-Si) based solar cells with around 70% of worldwide production. In order to improve the quality of the Si material, a proper characterization of the electrical activity in mc-Si solar cells is essential. A full-wafer characterization technique such as photoluminescence imaging (PLi) provides a fast inspection of the wafer defects, though at the expense of the spatial resolution. On the other hand, a study of the defects at a microscopic scale can be achieved through the light-beam induced current technique. The combination of these macroscopic and microscopic resolution techniques allows a detailed study of the electric…

Silicon quantum point contact with aluminum gate

2000

Fabrication and electrical properties of silicon quantum point contacts are reported. The devices are fabricated on bonded silicon on insulator (SOI) wafers by combining CMOS process steps and e-beam lithography. Mobility of 9000 cm2 Vs−1 is measured for a 60 nm-thick SOI film at 10 K. Weak localization data is used to estimate the phase coherence length at 4.2 K The point contacts show step like behaviour in linear response conductance at 1.5 K. At 200 mK universal conductance fluctuations begin to dominate the conductance curve. The effective diameter of quantum point constrictions of the devices are estimated to be 30–40 nm. This estimate is based on TEM analysis of test structures and A…

Kinetics of Bulk Lifetime Degradation in Float‐Zone (FZ) Silico n : Fast Activation and Annihilation of Grown‐In Defects and the Role of Hydrogen vs …

2020

Float-zone (FZ) silicon often has grown-in defects that are thermally activated in a broad temperature window (≈300–800 °C). These defects cause efficient electron-hole pair recombination, which deteriorates the bulk minority carrier lifetime and thereby possible photovoltaic conversion efficiencies. Little is known so far about these defects which are possibly Si-vacancy/nitrogen-related (VxNy). Herein, it is shown that the defect activation takes place on sub-second timescales, as does the destruction of the defects at higher temperatures. Complete defect annihilation, however, is not achieved until nitrogen impurities are effused from the wafer, as confirmed by secondary ion mass spectro…

Nanocrystal metal-oxide-semiconductor memories obtained by chemical vapor deposition of Si nanocrystals

2002

We have realized nanocrystal memories by using silicon quantum dots embedded in silicon dioxide. The Si dots with the size of few nanometers have been obtained by chemical vapor deposition on very thin tunnel oxides and subsequently coated with a deposited SiO2 control dielectric. A range of temperatures in which we can adequately control a nucleation process, that gives rise to nanocrystal densities of ∼3×1011 cm−2 with good uniformity on the wafer, has been defined. The memory effects are observed in metal-oxide-semiconductor capacitors or field effect transistors by significant and reversible flat band or threshold voltage shifts between written and erased states that can be achieved by …

Simulated and measured temperature coefficients in compensated silicon wafers and solar cells

2019

Abstract In this paper we perform a thorough investigation of the temperature coefficients of c-Si solar cells and wafers, based on both experimental data and device simulations. Groups of neighboring wafers were selected from different heights of four high performance multicrystalline silicon ingots cast using different dopants concentrations and Si feedstocks; Three different target resistivities of compensated silicon ingots based on Elkem Solar Silicon (ESS®), which are purified through a metallurgical route, and one non-compensated reference ingot. The wafers were processed into Al-BSF and PERCT type solar cells, as well as into lifetime samples subjected to selected solar cell process…

In situ measurement of the kinetic friction of ZnO nanowires inside a scanning electron microscope

2012

Abstract A novel method for measuring the kinetic friction force in situ was developed for zinc oxide nanowires on highly oriented pyrolytic graphite and oxidised silicon wafers. The experiments were performed inside a scanning electron microscope and used a nanomanipulation device as an actuator, which also had an atomic force microscope tip attached to it as a probe. A simple model based on the Timoshenko elastic beam theory was applied to interpret the elastic deformation of a sliding nanowire (NW) and to determine the distributed kinetic friction force.

Improving the material quality of silicon ingots by aluminum gettering during crystal growth

2016

We present a method for the purification of silicon ingots during the crystallization process that reduces significantly the width of the low charge carrier lifetime region at the ingot top. The back-diffusion of impurities from the ingot top is suppressed by adding a small amount of pure aluminum into the silicon melt right at the end of the solidification. We study the aluminum gettering effect by instrumental neutron activation analysis (INAA) and Fei imaging. Furthermore, we present a model for aluminum gettering of Fe in the silicon ingot that is in agreement with literature data for aluminum gettering at lower temperature. The distribution of iron in the ingots with and without alumin…

Numerical modelling of the industrial silicon single crystal growth processes

2007

Silicon wafers produced from the silicon single crystals are the basic material for the manufacturing of various kinds of electronic devices determining the everyday life of the modern society. Silicon single crystals industrially are mainly grown by two methods - by the Czochralski and by the floating zone technique. Both of them involve various physical processes with complex interactions which makes the experimental optimization of the growth techniques a rather hard and expensive task. Therefore, mathematical modelling supported by the rapid increase of the computer power has become an effective means in the development of the industrial crystal growth. (© 2007 WILEY-VCH Verlag GmbH & C…

CdTe Nanocrystal Synthesis in SiO 2 /Si Ion‐Track Template: The Study of Electronic and Structural Properties

2020

Impurity analyses of silicon wafers from different manufacturing routes and their impact on LID of finished solar cells

2013

Summarizes the measurements of impurity concentrations in directionally solidified silicon ingots from different feedstocks. The substitutional Carbon and interstitial Oxygen are measured on as-sawn wafers using FTIR. Active iron concentration is mapped on a-Si:H passivated wafers. It is observed that these impurities present in Elkem Solar Grade Silicon (ESS™) concentrations are comparable to the standard polysilicon which are in the acceptable ranges for silicon for solar industry. The measured LID of the finished solar cells is also comparable.